using clickhouse-local to analyze archived log files

at work we’re hoarding log files. it’s a low-cost, low-tech solution: btrfs, some python script archiving /var/log/*.log, *.1 from hundreds of servers. we have a peace of mind that whatever it is – as long as it’s logging to that folder – we’ll have an archive of it. till now, whenever there was a need ... Read More

ClickHouse – dictionary with string keys

i wanted to create a clickhouse dictionary that used String as a key, not an int. docs mention here: “A composite key can consist of a single element. This makes it possible to use a string as the key, for instance”. I’ve been trying this and failed few times. creation worked but i could not ... Read More

clickhouse – getting n most significant digits of a number

i’m testing some wild idea of finding matches in quite a large dataset. part of the problem is that scaling of input is unknown, 123 might be correct match for 1.23 or for 12.3. here’s an expression that returns me n=4 most significant digits of each float from the input array:


clickhouse is a column oriented OLAP database. i’ve started using it about half a year ago. i’m impressed. earlier i’ve read about it on percona’s blog but did not fully grasp how performant it was. i’ve tried it when i wrestling with MariaDB’s query planner on table with ~100M rows got me tired and each ... Read More